OTTAWA - The federal Conservatives are facing the same sort of questions about phoney donors as some of the players in Quebec municipal and provincial politics, prompting the Opposition to demand an investigation.

The allegations relate to a report by Postmedia News quoting several Montrealers who say they did not donate to the Conservatives in one riding even though party financial filings say they did.

On Friday afternoon, the Conservatives produced copies of cheques from seven individuals quoted in the article. Four of the amounts do not correspond with the donation logged by Elections Canada, but a party spokesman said cost deductions are taken when contributors buy tickets to fundraising events.

The Tories collected $288,823 in donations in the riding of Laurier-Sainte-Marie in 2009, despite placing fifth in the 2008 election. Much of the money was transferred to more promising ridings.

The Canadian Press reported earlier this year that $12,000 of the donations came from employees of three large engineering firms. All three firms have had employees arrested as part of a corruption crackdown on Quebec's construction industry.

The Charbonneau commission, an inquiry looking into the system, has already heard from one former construction boss about how he would hide large, illegal donations to political parties by funnelling them through employees and family members.

Under federal law, it is illegal to conceal the identity of a donor.

The NDP sent a letter to Elections Canada on Friday asking the agency to investigate the allegations in Laurier-Sainte-Marie. All three federal opposition parties raised the matter during question period in the House of Commons.

"Who really donated these thousands of dollars to the Conservatives. Engineering companies? And most of all, what did the Conservatives promise in exchange?" said New Democrat MP Alexandre Boulerice.

"In light of the revelations at the Charbonneau commission, can the government assure us the money didn't serve to obtain contracts with the federal government?" said Liberal MP Massimo Pacetti.

The Conservatives said Elections Canada had already signed off on their financials.

"All the details the honourable member is referring to have been given to Elections Canada, and it certified this information years ago," said Conservative MP Pierre Poilievre, parliamentary secretary to the transport and infrastructure minister.

Neither Elections Canada nor the RCMP would confirm or deny they were investigating the donations. Elections Canada is in the midst of a major probe into misleading phone calls placed to voters during the 2011 election, referred to as "robocalls."

The donations in Laurier-Sainte-Marie coincide with a major Conservative fundraiser held in May 2009 in a downtown Montreal hotel. Sen. Leo Housakos, himself an executive at an engineering firm at the time, was a key organizer of the event.

When asked why $1,000 cheques from four Montreal donors do not correspond to the $666 logged by Elections Canada, Conservative party spokesman Fred Delorey suggested it had to do with the cost of holding the event.

"When it comes to fundraisers, the Canada Elections Act requires that the cost of holding the event (room rental, napkins, etc) be deducted from the receipt issued for a donation," Delorey said.

Top Quebec engineering executives were put on the exclusive guest list for separate, smaller receptions at that 2009 event that included senior members of the federal cabinet, including then Public Works minister Christian Paradis.

The Senate ethics officer cleared Housakos of any suggestion of improper influence in the award of a federal contract in Montreal to a consortium that includes BPR, the firm he worked for in 2009.